1. Field of the Invention
This invention relates generally to the field of enclosures for housing electronics, and in particular to an enclosure for housing electronics which includes a fan tray assembly which may be easily removed from and inserted into the enclosure.
2. Description of the Related Art
Enclosures for housing electronic circuit boards are widely used in a variety of technologies, including telecommunications, industrial control, medical electronics, and military applications. As shown in prior art FIGS. 1 and 2, such enclosures 20 include a main compartment 22 for receiving a plurality of electronic circuit boards 24 in a side-by-side relation. Each of the circuit boards 24 electrically connects to a backplane at a rear of the main compartment. Conventional enclosures may further include a bottom compartment 26 beneath the main compartment 22, which bottom compartment may include one or more fan tray assemblies 28 for circulating relatively cool air surrounding the electrical enclosure into the main compartment to conduct heat away from the electronic circuit boards and main compartment.
Conventional enclosures may further include a cable tray 30 mounted on a front of enclosure 20. Cable tray 30 defines a trough for receiving electrical cables emanating from within the main compartment. The cable tray routes the cables to either side of, and away from, the enclosure 20. As seen in prior art FIGS. 1 and 2, the cable tray is mounted in front of, and spaced from, a front face 32 of enclosure 20, and cable tray 30 has an upper surface 34 below a bottom surface 36 of the main compartment 22. The cable tray 30 is mounted below bottom surface 36 so as not to interfere with the circuit boards 24 as they are inserted into and taken out of main compartment 22.
A difficulty resulting from this construction is that the cable tray 30 lies in front of the fan tray assemblies 28 in the bottom compartment 26. Lying in front of the fan tray assemblies, the cable tray largely obstructs access to the fan tray assemblies and makes it difficult to insert the fan tray assemblies and to remove the fan tray assemblies. Unfortunately, owing to their continual operation, frequent maintenance of the fan trays of the fan tray assemblies is required.
One solution to the difficulty in accessing the fan tray assemblies is found in German Utility Model No. DE 20 2004 004 198 U1 to Appenzeller and Rademacher GmbH, Daun, Germany. That reference discloses that the cable tray is mounted for translation up and down at the front of the electrical enclosure. Thus, when it is desired to access the fan tray assemblies behind the cable tray, the cable tray translates upward away from the fan tray assemblies, and one or more of the fan trays may then be slid straight out from the bottom compartment. A problem with this solution is that the front of the main compartment is often crowded with cables, and it is often difficult or impossible to raise the cable tray a sufficient amount to slide the fan tray(s) out.
Conventional fan tray assemblies further include one or more fan filters for filtering the air drawn into the main compartment by the fan trays. These fan filters tend to get clogged with airborne particles. In conventional electrical enclosures, the cable tray in general at least partially obstructs access to the fan filter as well as the fan trays. And in systems where the fan filters are not obstructed by the cable tray, the fan filters slide straight out from the bottom compartment. In sliding straight out, the fan filters often scrape against the bottom surface of the fan trays. Contact with the filter often dislodges particles and debris trapped by the filter, and these particles and debris may then be drawn into the main compartment, thus defeating the purpose of the fan filters.